This research is an investigation of the biosynthesis of estrogens and other steroid hormones, and the interrelationships between human development and steroid hormones. It aims also to develop useful biochemical and analytical methods of clinical applicability. Our immediate objectives are: (1) to elucidate the steric, kinetic, and electronic mechanisms of aromatization and lyase reaction by human steroid hormone synthesizing systems, (2) to elucidate pathway(s) through which hydroxylated estrogens are formed, (3) to isolate sex steroids and their conjugates and study the mode of conjugation and excretion, (4) to elucidate steroid conformations and (5) to purify and characterize aromatase in order to further our understandings of endocrine processes at the molecular level. The methods are synthesis of steroids with and without deuterium tritium, carbon-13, carbon-14 and oxygen-18 labels at stereoselective and/or regiospecific positions, conformational analysis by X-ray crystallography and spectroscopy, chemical and biochemical distribution analysis of isotopes, incubations with various enzyme preparations and tissue homogenates of combinations of regio- and stereoselectively labeled steroids, and analyses of the products, kinetics and dynamic intermediates. A neutral resin, steady state distribution machine, chromatographies, nmr and mass spectrometry are used for the isolation and characterization of steroids and their conjugates.